I love a book with a hook. (And no, I didn’t plan on the rhyme.)
Mary Amatos has a great one. In Please Write in This Book, a teacher leaves out a blank journal. She encourages kids to write basically anything they want. The entire novel is the kids’ back-and-forth observations, which turn into conflict. The kids record the conflict and use the book, and some old-fashioned cooperation, to arrive at an agreement.
It’s funny and inventive. The entire narrative is kids expressing themselves through their own writing. The novel has lots of white space, which my daughter used to write her own reactions to the conflict. She thought it was cool to feel like a participant in the story. (Thankfully it wasn’t a library book.)
One observation: In too many middle-grade books, the main boy is funny, and the main girl is serious and worried about the rules. Sure, contrasting personalities help build conflict, and of course I could write a list of exceptions. But I love books that rip up the sugar-and-spice-and-everything-nice image of girls. That was the goal for my unpublished novel The Graham Cracker Plot.